Process for cleaning surfaces using dry ice

Abstract

Metal surfaces may be cleaned using a dry ice (CO 2 ) blasting processes. Once cleaned, the surfaces are ready to be painted. The process of this invention is especially useful on ships where there are numerous metal surfaces that are subject to dirt and corrosions. The proper operating parameters for each of the types of metal surfaces require exacting conditions. These parameters include the size of the dry ice pellets, the discharge rate of the ice pellets, the type of nozzle being used and the flow rate of the pellets, the pressure of the pellets leaving the nozzle. The dry ice cleaning processes of the present invention eliminates secondary waste streams and moisture, leaving the treated surfaces immediately ready for painting. Only the dirt, loose paint, debris and other surface contaminants removed during the dry ice cleaning process need to be cleaned up prior to preservation and/or painting and return to service.

1 . A process for cleaning metal surfaces having loose paint, debris and contaminants thereon comprising:
 (a) blasting said metal surface with an amount of dry ice pellets sufficient to dislodge at least a substantial portion of the dirt, loose paint, debris and contaminants from said metal surface to provide a clean metal surface; and   (b) removing said dislodged dirt, loose paint, debris, and contaminants from said cleaned surface.   
     
     
         2 . The process according to  claim 1  further comprising painting said clean metal surface. 
     
     
         3 . The process according to  claim 2  wherein said metal surface is a member of the group consisting of vertical package conveyors (VPC), exterior deck and non-skid areas, bilges, potable water tanks, electrical switchboards and electrical components, jet blast deflectors, gas turbine engines, various elevators and fire damaged spaces 
     
     
         4 . The process according to  claim 1  wherein said metal surface is a ferrous metal. 
     
     
         5 . The process according to  claim 1  wherein said ferrous metal is a member of the group consisting of iron and stainless steel. 
     
     
         6 . The process according to  claim 1  wherein said metal surface is a non-ferrous metal. 
     
     
         7 . The process according to  claim 1  wherein said non-ferrous metal is selected from the group consisting of aluminum, copper/nickel alloys and inconel alloys. 
     
     
         8 . The process according to  claim 1  wherein said dry ice pellets have a diameter between about 2.5 mm and about 3.5 mm. 
     
     
         9 . The process according to  claim 1  wherein said dry ice pellets have a diameter between about 2.8 mm and about 3.2 mm. 
     
     
         10 . The process according to  claim 1  wherein said dry ice pellets are supplied from a feed system having an air compressor operating a pressure of 50 to about 250 psi by passing said pellets from the air compressor through an accompanying high pressure hose and nozzle at a flow rate of up to 500 ft 3 /min. 
     
     
         11 . The process according to  claim 1  wherein said dry ice pellets are supplied from a feed system having an air compressor operating at a flow rate of between about 200 ft 3 /min to about 300 ft 3 /min. 
     
     
         12 . The process according to  claim 1  wherein said dislodged loose paint, debris, and contaminants are removed from said cleaned metal surface using a vacuum. 
     
     
         13 . The process according to  claim 1  wherein said blasting is accomplished using a nozzle sweep of from about 8 ft 2 /min to about 12 ft 2 /min. 
     
     
         14 . A process for cleaning ferrous or non-ferrous metal surface having dirt, loose paint, debris and contaminants thereon comprising:
 (a) blasting said metal surface with dry ice pellets said dry ice pellets having a diameter between about 2.5 mm and about 3.5 mm at a pressure between about 50 to about 250 psi by passing said pellets from the air compressor through an accompanying high pressure hose and nozzle at a flow rate of up to 500 ft 3 /min. to dislodge at least a substantial portion of the loose paint, debris and contaminants from the metal surface to provide a clean metal surface;   (b) removing said dislodged loose paint, debris, and contaminants from said cleaned surface; and   (c) painting said clean metal surface.   
     
     
         15 . The process according to  claim 14  wherein said dry ice pellets have a diameter between about 2.8 mm and about 3.2. 
     
     
         16 . The process according to  claim 14  wherein said dry ice pellets are supplied from a feed system having an air compressor operating at a flow rate of between about 200 ft 3 /min to about 300 ft 3 /min. 
     
     
         17 . The process according to  claim 14  wherein said dislodged loose paint, debris, and contaminants are removed from said cleaned metal surface using a vacuum.